An electromagnetic friction disk clutch which is known from the prior art comprises, inter alia, a rotor, an electromagnet and an armature disk. When the electromagnet is switched on, a magnetic field is formed, and results in the armature disk being pulled against the rotor. When the electromagnet is switched off, the attraction force thus disappears, the armature disk is disconnected from the rotor by means of a spring element, and is returned to the disengaged clutch position. In the disengaged position, the armature disk is separated from the rotor by an air gap. This air gap must, on the one hand, be as small as possible so that the forces caused by the magnetic field are as large as possible, while, on the other hand, the air gap should be sufficiently large that it prevents the armature disk from inadvertently striking the rotor, for example as a result of axial oscillations occurring, during operation. The friction between the armature disk and the rotor resulting in the armature disk being repeatedly pulled against the rotor results in wear, which leads to an enlarged air gap between the two friction partners in the disengaged state. This results, on the one hand, in the spring force to overcome the air gap rising while, on the other hand, the force acting on the armature disk as a result of the magnetic field decreasing considerably as the air gap becomes larger, so that the torque which can be transmitted falls. In the extreme, this leads to loss of function of the friction disk clutch.
This undesirable effect can be partially compensated for by using a spring with a degressive spring characteristic. Nevertheless, even a spring with a degressive spring characteristic leads to the torque which can be transmitted falling considerably as the air gap becomes ever larger, with the clutch losing its intended functionality.